rhizoverbBeta
DictionaryastigmatismUneven eye curvature
noun

astigmatism

uh-STIG-muh-tiz-um/əˈstɪɡmətɪzəm/

Uneven curvature of the eye that causes blurred or distorted vision.

Astigmatism prevents incoming light from meeting at a single retinal focus.

Educational eye cutaway showing uneven corneal curvature and light rays failing to meet at a single retinal focus, no labels.
Etymology
aGreekwithout
+stigmatGreekmark, spot, point
+ismEnglishcondition

The name combines “without” and “point”: light rays fail to converge at a single point on the retina. It names the focusing result of the eye’s imperfect curvature.

In context

NASA Night Sky Network105:52
most of your optical defects in your vision don't lie astigmatism generally lies around the outside portion of your eye for instance so your visual acuity will be increased substantially
Global Moon Party - Kickoff International Observe the Moon Night

More examples

  • The eye examination detected mild astigmatism.
  • With astigmatism, distant and nearby objects may both appear distorted.
  • The prescription accounts for her astigmatism as well as nearsightedness.

Forms

astigmatic adjective — Having or relating to astigmatism.

Similar words

nearsightedness
Primarily blurs distant objects rather than causing directional distortion.
farsightedness
Often makes near focusing difficult through a different optical problem.